A hole can be introduced into a knitted fabric by pairing a
yarn over stitch with a nearby (usually adjacent)
decrease. If the decrease
precedes the yarn over, it typically slants
right as seen from the right side (e.g., k2tog,
not ssk; see
knitting abbreviations). If the decrease
follows the yarn over, it typically slants
left as seen from the right side (e.g., k2tog tbl or ssk,
not k2tog). These slants pull the fabric away from the yarn over, opening up the hole. Pairing a yarn over with a
decrease keeps the stitch count constant. Many beautiful patterns separate the yarn over and decrease stitches, e.g., k2tog, k5, yo. Separating the yarn over from its decrease "tilts" all the intervening stitches towards the decrease. The tilt may form part of the design, e.g., mimicking the veins in a leaf. There are few constraints on positioning the holes, so practically any picture or pattern can be outlined with holes; common motifs include leaves, rosettes, ferns and flowers. To design a simple lace motif, a
knitter can draw its lines on a piece of knitting graph paper; right-slanting lines should be produced with "k2tog, yo" stitch-pairs (as seen on the right side) whereas left-slanting lines should be produced with "yo, k2tog tbl" (or, equivalently, "yo, ssk" or "yo, skp") stitch pairs (again, as seen on the right side). More sophisticated patterns will change the grain of the fabric to help the design, by separating the yarn overs and
decreases. It is common for lace knitters to insert a "lifeline", a strand of contrasting yarn threaded through stitches on the needle, at the end of every pattern repeat or after a certain number of rows. This allows the knitter to rip out a controlled number of rows if a mistake is discovered. ==History and comparison to other laces==